Starch is composed primarily of two components: amylose, a mainly linear polymer of about 500-6000 xcex1-D glucosyl residues, and amylopectin, a highly branched polymer of xcex1-D glucosyl distributed in 15-60 residues per chain (Godet et al., Carbohydrate Polymers 27:47-52 (1995)). It is well known that amylose can form complexes with molecules such as iodine, alcohols and lipids, whereas amylopectin forms these complexes weakly or not at all (Morrison et al., Cereal Chem 70:385-91 (1993); Sarko and Zugenmaier, Fiber Diffraction Methods, A. D. French and K. C. Gardner, Eds., ACS Symposium Series 141:459-482 (1980)). The in situ biosynthesis of amylose-lipid complexes in starch with naturally occurring fatty acids and phospholipids has been demonstrated (Morrison et al. (1993)). Others have shown that complex formation occurs during heat/moisture treatments, especially during gelatinization of starches with the naturally containing lipids (Kugimiya et al., Stxc3xa4rke 32:265-270 (1980); Kugimiya and Donovan, J. Food Sci. 46:765-777 (1981)) or when lipids are added to defatted starches (Biliaderis et al., Food Chem. 22:279-295 (1986)) or pure amylose which is free of natural lipids (Biliaderis et al, Carbohydr. Polym. 5:367-389 (1985)).
Both naturally-occurring and heat-formed complexes show specific properties such as a decrease in amylose solubility or an increase in gelatinization temperatures (Eliasson et al., Stxc3xa4rke 33:130 (1981), Morrison et al. (1993)). Polar lipids, e.g., fatty acids and their monoglyceride esters are of technological importance in starch systems, as they cause a reduction in stickiness, improved freeze-thaw stability (Mercier et al., Cereal Chem. 57:4-9 (1980) and retardation of retrogradation. One important example is the use of fatty acids and monoglycerides as anti-staling agents in bread and biscuits. Incorporation of such additives in the dough induces a slower crystallization (retrogradation) of the amylose fraction and retards the staling of bread (Krog, Stxc3xa4rke 22:206-210 (1971)).
The present invention pertains to starch-emulsifier compositions and methods of making the starch-emulsifier compositions comprising heating starch (e.g., jet-cooking, heating in a batch cooker) in the presence of an emulsifier to produce a starch-emulsifier dispersion which can optionally be treated to obtain greater than about 20% by weight short chain amylose.
In one embodiment of the invention, a starch and an emulsifier are heated (e.g., jet-cooked) to disrupt essentially all starch granules and solubilize amylose and amylopectin in the starch. The product contains a dispersion of gelatinized starch and emulsifier which is believed to be in the form of a complex, as seen by X-ray diffraction. The dispersion of starch and emulsifier can be cooled slowly or quickly to form an elastic textured paste, or the solution can optionally be dried to a powder.
In another embodiment of the invention, a starch and emulsifier are heated (e.g., jet-cooked) to produce a dispersion of gelatinized starch and emulsifier in which the amylose and amylopectin are solubilized. The starch is subsequently hydrolyzed to release short chain amylose, preferably using an enzymatic treatment. After hydrolysis of the starch-emulsifier solution, the solution can optionally be heated to a temperature sufficient to liquify the emulsifier, thereby increasing the percentage of starch-emulsifer complex formed. Thereafter, the solution can be cooled to form a short-textured, non-elastic paste or it can optionally be dried (e.g., by spray drying) into a powder.
The starch-emulsifier compositions can also be optionally co-processed with hydrocolloids, polymers, gums, modified starches and combinations thereof, which can be added at any point in the processes described herein. These optional ingredients serve to change (e.g., increase or decrease) the functional properties (e.g., water binding capacity, oil binding capacity or viscosity) of the composition depending upon product end use. For example, these optional ingredients can be added to increase the overall water binding capacity of the starch-emulsifier composition or change the rheology of the starch-emulsifier composition.
The starch-emulsifier composition produced by a process which uses a hydrolytic method is characterized by a relatively small particle size (a weight average of 4-5 xcexc), a short, non-elastic texture or rheology and a low water and oil binding capacity. The starch-emulsifier composition produced by cooking starch and emulsifier, without subsequent hydrolysis, is characterized as more elastic and a less opaque gel compared to the hydrolyzed product. In either process, the dried starch-emulsifier composition can be rehydrated, preferably in an aqueous medium suitable for use in food or beverage formulations (e.g., milk or water), under conditions of medium to high shear to produce an opaque paste upon refrigeration.
The starch-emulsifier compositions produced by the methods described herein are useful in a variety of food and beverage applications. For example, the starch-emulsifier compositions can be used as an opacifier in foods and beverages such as skim milk, or as a texturizing agent to prepare dairy products with a rheology similar to sour cream, yogurt, mayonnaise and similar products. For example, the starch-emulsifier compositions of the present invention can be used to prepare lactose-free dairy products. The starch-emulsifier compositions can also be used to stabilize foams, such as in the production of ice cream, and as a fat replacer in a variety of reduced-fat and fat-free foods, such as cakes, pudding type desserts, sauces, margarine, cream cheese and other spreads, snack dips, mayonnaise, sour cream, yogurt, ice cream, frozen desserts, fudge and other confections, and skim milk. The starch-emulsifier compositions can be incorporated into fat-free, reduced fat and fat containing cheeses, such as natural, processed and imitation cheeses in a variety of forms (e.g., shredded, block, slices, grated). The starch-emulsifier compositions are also useful, as for example a shortening, in baked goods such as cakes, pies, brownies, cookies, breads, noodles, snack items, such as crackers, graham crackers and pretzels, and similar products.
The present invention pertains to methods of manufacture and the starch-emulsifier compositions produced thereby that are useful in a variety of food and beverage applications. According to the invention, a starch is heated in the presence of an emulsifier to a temperature and pressure sufficient to disrupt essentially all the starch granules and solubilize the amylose and amylopectin contained therein, such as by jet cooking, to yield a starch-emulsifier dispersion. This dispersion can be cooled slowly or quickly to form an elastic gel, or the dispersion can optionally be dried to a powder. The powder can be rehydrated with medium to high shear to produce a smooth gel that is more elastic and less opaque compared to the hydrolyzed product described below.
Alternatively, a dispersion of the starch-emulsifier complex produced as described above can be treated to generate about 20% by weight short chain amylose (e.g., enzymatically debranched, hydrolysis of the backbone by amylase or acid hydrolysis), and the resultant dispersion of starch, containing greater than about 20% by weight short chain amylose, and emulsifier is optionally heated to a temperature sufficient to inactivate the enzyme if used and to liquify the emulsifier. Liquification of the emulsifier facilitates the formation of additional starch-emulsifier complexes in the final composition.
As used herein, short chain amylose is defined as amylose having a degree of polymerization (DP) of from about 6 to about 60 and a molecular weight of from about 1,000 to about 10,000 which is indicative of maltodextrin. The term xe2x80x9cgelatinizationxe2x80x9d or varient thereof, is intended to embrace the generally recognized term but also is intended to encompass the process of rupturing essentially all starch granules present in the starch, thereby releasing amylose and amylopectin.
The dispersion of starch and emulsifier containing about 20% short chain amylose can be allowed to cool to form an opaque paste with a short, non-elastic texture. Alternatively, the dispersion can be dried to a powder and rehydrated with medium to high shear to produce a short, smooth, non-elastic textured paste of high opacity upon refrigeration.
The starch used as a starting material in the process of the present invention can be a native starch or a pregelatinized starch. If a pregelatinized starch is utilized, it should preferably contain a low amount of resistant starch, such as less than about 10% resistant starch. If the starting starch has more than about 10% resistant starch, the starch can be used in the present invention if it is first heated to a temperature above the melting point of the resistant starch.
The native or pregelatinized starch used in the present invention should preferably have an amylose content of less than about 30%. If the amylose content is greater than about 30%, debranching and/or hydrolysis of the starch (e.g., with an acid or by enzymatic amylase treatment) prior to heating in the presence of the emulsifier may be required to reduce the molecular weight of the amylose. The use of high-amylose starch is generally not preferred, as high-amylose starch tends to form stable resistant starch with a large particle size during processing. For example, debranched or partially hydrolyzed amylomaize can be used, as well as common cornstarch, potato, tapioca, wheat, smooth pea, rice, sago, barley and oat starches.
Without wishing to be bound by theory, it is believed that the processes described herein yield compositions comprising starch and emulsifier in the form of a complex having an insoluble microparticle nature which is stabilized by the interaction between amylose and emulsifier. The composition also comprises uncomplexed emulsifier, uncomplexed starch, and optionally short chain amylose if debranching and/or hydrolysis is performed. Thus, emulsifiers capable of forming a complex with amylose are particularly preferred for use in the invention. Generally, the emulsifiers will be monoglycerides, sorbitan esters, diacetyl tartaric acid esters of monoglycerides (DATEM), propylene glycol esters, enzyme modified lecithin (EML), polysorbates and sucrose esters of medium and long chain saturated fatty acids (e.g., having an acyl group containing more than about 10 carbon atoms), as well as saturated fatty acids (e.g., saturated fatty acids which contain from about 12 to about 18 carbons) and unsaturated fatty acids (unsaturated fatty acids which contain from about 12 to about 18 carbons, e.g., oleic and linoleic acids). For example, emulsifiers including, but not limited to, polyethylene glycol monolaurate or glyceryl monostearate, sodium or calcium stearoyl-2-lactylate, polyoxyethylene sorbitan monostearate, sucrose monostearate and sucrose monopalmitate are suitable for use in the starch-emulsifier composition of the present invention, as well as other saturated fatty acids (see also Example 6). EML can be produced by treating lecithin with phospholipase A2. EML produced through the action of phospholipase A2 is enriched in lysophosphatydylcholine, which is known to form complex with amylose. Commercial EML is available at Lucas Meyer Inc. (Decatur, Ill.) and Central Soya Co. (Fort Wayne, Ind.).
The starch and the emulsifier are combined in an aqueous medium such as water to produce a dispersion. The dispersion generally contains from about 5% to about 25% (w/w) of starch. The emulsifier will be present in an amount which is approximately 0.1% to about 25% of the starch weight, and more preferably 1% to 10% of the starch weight present in the composition. The dispersion is then heated under conditions appropriate to disrupt essentially all the starch granules and solubilize the amylose and amylopectin present in the starch. This can be carried out, for example, by co-jet cooking the starch-emulsifier dispersion. Alternatively, the starch-emulsifier dispersion can be heated in a reactor or batch cooker, or by any other method in which the starch is gelatinized in the presence of the emulsifier, such as by extrusion. The starch can also be jet cooked into the emulsifier; that is, the starch can be heated to or above its gelatinization temperature and immediately combined with the emulsifier. The emulsifier may need to be dispersed beforehand in a little water and the dispersion added to the starch slurry prior to cooking; added to the jet cooked starch; or the starch is jet cooked into the dispersion of the emulsifier. The temperature and pH necessary to disperse the emulsifier in water are characteristic for each emulsifier or can be determined by those skilled in the art. It is essential that the emulsifier and starch be combined prior to the heating or jet cooking step or immediately after solubilization of the starch, as later addition of the emulsifier results in a larger particle size and a gritty product due to retrogradation of the starch.
In one embodiment, after the starch-emulsifier dispersion is heated to solubilize the amylose present in the starch, the starch is treated to release short chain amylose. Appropriate treatment of the starch will result in a starch material containing greater than about 20% short chain amylose. Generally, release of the short chain amylose from the starch will be carried out by enzymatically debranching the starch, e.g., the starch can be debranched with (1-6)-specific glycosidic enzymes which are capable of cleaving 1,6-alpha-D-glucosidic linkages. For instance, the starch-emulsifier dispersion can be treated with pullulanase or isoamylase, at a temperature and pH and for a time sufficient to allow the enzyme to release the short chain amylose. Generally, appropriate temperatures will range from about 25xc2x0 C. to about 100xc2x0 C., with from about 55xc2x0 C. to about 65xc2x0 C. being preferred, for a time of from about 1 hour to about 30 hours, depending on the enzyme utilized and the enzyme concentration. Furthermore, the pH of the solution will be from about 3 to about 7.5. In a particularly preferred method, the starch-emulsifier dispersion is treated with pullulanase at 60xc2x0 C. at pH 5 for about 4 hours. The optimum conditions for the enzymatic reaction will vary, with changes in parameters such as starch and enzyme concentrations, pH, temperature and other factors which can be readily determined by the skilled artisan.
Alternatively, the starch can be randomly hydrolyzed to produce greater than 20% short chain amylose by use of an appropriate acid, such as a mineral acid or organic acid. Generally, acid hydrolysis will take place at a pH of less than about 4xc2x0 C. and at a temperature greater than about 60xc2x0 C., depending upon the acid used. The conditions for acid hydrolysis should be such that inappropriate side reactions are minimized. Short chain amylose can also be generated by treating the starch with alpha amylase, alone or in combination with pullulanase. Substantial debranching or hydrolysis of the starch (e.g., debranching sufficient to generate a starch material containing greater than about 20% short chain amylose) results in a short textured, non-elastic paste, whereas in the absence of debranching or hydrolysis the product is an elastic gel (see Example 3).
Both the hydrolyzed and non-hydrolyzed starch-emulsifier dispersions can be heated to a temperature and pH and for a time sufficient to liquify the emulsifier, i.e., a temperature above the melting point of the emulsifier, to produce additional starch-emulsifier complexes in the composition. If a debranching enzyme is used, the heat treatment will also inactivate the enzyme. In most cases, a temperature of approximately 70xc2x0 C. to approximately 100xc2x0 C. is sufficient to liquify the emulsifier within the dispersion and inactivate the enzyme, if present. The starch-emulsifier dispersion can be heated by a number of conventional methods, including a heat exchanger, jacketed reactor, direct steam injection or extruder.
The starch-emulsifier compositions that have been hydrolyzed and subsequently heat treated appear watery and have a low viscosity at approximately 10% to 25% solids. The low viscosity product can be cooled slowly or rapidly to form a paste for use in food applications, or the low viscosity composition can be optionally dried to produce a powder by a number of art-recognized methods, including spray drying, belt drying, freeze drying, drum drying or flash drying; however, in a preferred embodiment, the dispersion is spray dried. The powder can be stored at room temperature, and can be rehydrated with water or another aqueous medium, preferably an aqueous medium which is appropriate for use in food and beverage formulations, under conditions of medium to high shear to give a paste of high opacity and short, non-elastic texture.
The starch and emulsifier can also be co-processed with hydrocolloids, gums, polymers, modified starches and combinations thereof to change the rheology or increase the water binding capacity of the starch-emulsifier compositions. For example, xanthan gum, alginate, carrageenan, carboxymethyl cellulose, methyl cellulose, guar gum, gum arabic, locust bean gum and combinations thereof can be added to the starch-emulsifier compositions at any time during the preparation thereof, as long as the additional ingredient(s) does not prevent the formation of the amylose-emulsifier complex. That is, these additional optional ingredients can be jet-cooked along with the starch and emulsifier, added prior to or after the debranching step, added prior to or after the optional heating step, added to the paste composition or dry blended with the powdered composition after drying. Preferably, the hydrocolloid, gum, modified starch or polymer is added to the dispersion after the debranching step and prior to drying the composition (see Example 7) or is dry blended with the powdered composition after the drying step.
The starch-emulsifier compositions of this invention comprise starch-emulsifier complexes, uncomplexed emulsifier, uncomplexed starch and optionally greater than from about 20% short chain amylose if the uncomplexed starch in the composition is hydrolyzed. The percentage of complex present in the composition will vary depending upon whether the starch and emulsifier are hydrolyzed, but in any event, the composition should comprise a minimum of about 20% by weight starch-emulsifier complex. The complexes are insoluble microparticulates which have an average particle size of less than about 10 xcexc, and preferably less than about 6 xcexc. The starch-emulsifier composition of the present invention produced using hydrolysis has a short, non-elastic texture or rheology and a low water and oil binding capacity and contains greater than about 20% short chain amylose. The starch-emulsifier composition produced by cooking starch and emulsifier, without subsequent hydrolysis, is characterized as a more elastic and less opaque gel compared to the hydrolyzed product.
The starch-emulsifier compositions of the present invention are suitable for use in a variety of foods and beverages. The amount of starch-emulsifier composition incorporated into the food or beverage will depend upon the formulation of the food, but will generally be approximately 1-10% by weight. For example, the starch-emulsifier compositions can be used as an opacifier in milk and similar foods to improve the visual appeal of the food. The starch-emulsifier compositions can also be used as a texturizing agent in various dairy foods; due to its small particle size, the starch-emulsifier compositions do not impart a gritty mouthfeel to products in which it is incorporated. The starch-emulsifier compositions are useful for preparing dairy products with a rheology similar to traditional sour cream, yogurt and mayonnaise formulations. For example, the starch-emulsifier compositions can be used in the preparation of lactose-free dairy products. The compositions are particularly useful for the preparation of reduced-fat and fat-free food products, particularly margarines, pudding type desserts, sauces, snack dips, mayonnaise, sour cream, yogurt, ice cream, frozen desserts, cream cheese and other spreads, fudge and other confections, and skim milk. The starch-emulsifier compositions can be incorporated into fat-free, reduced fat and fat containing cheeses, such as natural, processed and imitation cheeses in a variety of forms (e.g., shredded, block, slices, grated). The starch-emulsifier compositions are also useful in baked goods such as breads, cakes, pies, brownies, cookies, noodles, snack items, such as crackers, graham crackers and pretzels, and similar products, as it does not interfere with the organoleptic properties of the foods in which it is incorporated.
Terms used herein have their art-recognized meaning unless otherwise defined. The teachings of references referred to herein are incorporated herein by reference. All percentages are by weight unless otherwise specified.